1. Field of the Invention
The present invention relates to a printed wiring board.
2. Description of the Prior Art
In general, wiring patterns are formed on the front and back surfaces of a substrate for signal lines in a printed wiring board. The signal lines on the front and back surfaces are connected to each other through a via penetrating through the substrate, for example. A ground via is also formed outside the via for the signal lines. The ground via is coaxial with the via for the signal lines. Coaxial cable lines are established in the substrate in this manner. The ground via serves to trap noise of the signal lines.
Proposed is a so-called multilayered printed wiring board. Double-sided wiring boards are overlaid on one another in sequence. If the aforementioned coaxial vias are formed in such a multilayered structure, the ground via prevents connection between signal lines inside the multilayered wiring board because the ground via surrounds the via for signal lines. However, a high-speed signal transmission cannot be realized without the ground via.